辐射驱动中心点火靶丸的辐射源整形

Radiation pulse shaping for laser indirect-drive central ignition target

利用数值模拟的方法研究了辐射驱动中心点火靶丸辐射脉冲的整形方法。根据文献对于燃料低熵压缩冲击波匹配要求的描述,设计了一个四台阶型的驱动脉冲。发现在冲击波汇聚后,燃料内的强稀疏使得烧蚀面产生额外的强冲击波,导致靶丸的熵增较大,不能满足要求。设计了三台阶加两折线形式的脉冲曲线,利用第4个冲击波的时间及强度变化抑制了稀疏波,避免额外的强冲击波产生,很好地抑制了熵增。还描述了为了避免烧蚀层烧穿而过早关闭辐射源,导致燃料压缩密度下降的问题。三台阶加两折线形式的脉冲通过控制峰值温度的时间,解决了此问题,使燃料达到很好的压缩效果。

Radiation pulse shaping for indirect-drive laser fusion ignition targets was studied in detail with numerical simula- tion. A ＂four-step＂ pulse was shaped first, according to the description of Lindl about low-entropy compression of DT fuel, requi- ring that the DT ice is compressed by four shocks that coalesce near the inside surface of the fuel. But the fuel entropy is quite high driven with this pulse. The causation is that an additional strong shock is produced during the acceleration phase. Then a new pulse was shaped to compress the fuel well. It includes three steps and rises to top temperature by two slopes. This pulse changed the time and the pressure of the fourth shock, which could effectively avoid the production of the additional strong shock. The en- tropy increase which happens because of terminating the pulse too early in order not to ablate the ablator too much is also de- scribed in this work. The new pulse presented here resolves this problem well by controlling the time when the pulse reaches the top temperature.